Afocal relay lens system



May 2, 180! V; 3,317,265

AFOCAL RELAY LENS SYSTEM Filed Dec. l9, 1963 :OBJECT PLANE ATTORNEYUnited States Patent 3,317,265 AFOCAL RELAY LENS SYSTEM Guy V. Coniglio,Rochester, N.Y., assignor to Bausch & Lomb Incorporated, Rochester,N.Y., a corporation of New York Filed Dec. 19, 1963, Ser. No. 331,779 2Claims. (Cl. 350-46) ABSTRACT OF THE DISCLOSURE A fixed focus afocalrelay lens system having a magnification of substantially 5x for use onoptical measuring projectors where increased magnification is required.

The present invention relates to a relay lens system and moreparticularly it relates to an image magnifying afocal type of opticalsystem.

Because of the continued development of miniaturization programs inindustry, optical instruments are required to work at much highermagnification than heretofore. The necessary increase in magnifyingpower does not create any sizeable problem in some types of opticalsystems but it may present a consider-able problem in others. A problemis presented, for instance, when it is necessary to provide a boostermagnification as an auxiliary device for a contour or measuringprojector by rea son of the fact that a distortionless image is a primenecessity along with the desired high magnification and along with anexcellent state of all chromatic and monochromatic image aberrations.

In view of the above-mentioned considerations, it is an object of thepresent invention to provide an afocal relay lens system having an imagemagnification of 5X, said image being free of distortion and furthermorehaving an excellent correction for coma and astigmatism as well asspherical and chromatic aberrations.

It is a further object to provide such a device which'is constructed ofsimple and low-cost optical parts which are so arranged and constructedto produce an exact specified magnification while achieving a nearoptimum state of correction.

Other objects and advantages will be apparent from a study of thespecification herebelo-w taken in connection with the accompanyingdrawing having a single figure which generally illustrates a preferredform of the invention.

The optical system according to this invention is generally designatedbythe numeral and it is composed of a sequence of optically aligned lensesand lens elements which are numbered from I to VII beginning at theentrant side of said system and which together form an afocal opticalsystem having a magnification of 5X for the image produced thereby. Theoptical system is char acterized by two groups of lenses, the frontgroup being designated G and the rear group being designated G these twogroups being separated by a long axial air space which is the sum of thefocal lengths of both groups.

Starting at the object plane, parallel light enters a front doubleconvex positive singlet lens designated 1, the air space between theobject plane and lens I being designated S Closely spaced rearwardly oflens I is a doublet lens of positive power which is composed of anegative menis- Patented May 2, 1967 cus front lens element II and adouble convex positive lens element III which lies in contact with lenselement II. A small air space between the singlet lens I and saiddoublet lens is designated S Spaced by a distance designated Srearwa-rdly of said doublet lens is a pair of meniscus lenses which arelocated at the rear end of group G the meniscus front lens beingpositive in power and being designated IV and the rear lens beingdesignated V and being of negative power. The air space between the twomeniscus lenses is designated S For best performance, it has beendetermined that the values of spaces S S and S should bear the followingmathematical relationship to each other substantially.

The air space between the lens groups G G is designated S and rearwardlythereof is provided a second double convex positive singlet lensdesignated VI which is separated by a space designated S from a thirddouble convex singlet lens which is designated VII. Rearwardly of lensVII the image rays are collimated and extend through the air spacedesignated S7 to the image plane. As aforementioned, space S is adjustedto obtain a precise magnification of 5 X and it is also necessary tocoincidentally adjust the air space S so as to maintain proper afocalityof the optical system when making other adjustments.

The axial thicknesses of the lens elements I to VII are designatedrespectively from the front of the system as t to t and the focal lengthof the front group of lenses G is designated by F and serves as aparameter for the measurement of the other construction-a1 properties ofthe lens system 10. The radii of the successive refractive surfaces ofthe aforesaid lens elements numbering from the front of the opticalsystem are designated R to R It is of importance that the form of thelens system as above outlined is so chosen as to not only the adjustableafter installation so as to produce an exact magnification of 5 X foruse in critical measuring in contour projectors but it is also a purposeof this invention to construct the various lens elements in as simple aform as consistent with superior optical performance when used togetherin the optical system. Therefore, three simple singlet double convexlenses are provided having low curvatures on their refractive surfacesand lens VI being a symmetrical construction for advantages in low-costmanufacture. For the same reason, all of the positive lens elements I,III, VI, VII excluding positive lens element IV have been specified asbeing made from the same glass. For the proper correction of achromaticand monochromatic image aberrations, the refractive index of the glassesin the aforesaid positive lenses is specified with such a value that itis exceeded by at least .170 by the refractive index value of thenegative lens II and is exceeded by at least .092 by the value ofrefractive index of either of the meniscus lenses IV or V.

With particular reference to the focal lengths of the respective lenses,the values thereof are given in the table of mathematical expressionsherebelow in which the focal lengths of the double convex singlet lensesI, VI and VII are designated respectively, F F and F the focal length ofthe doublet lens is designated P and the focal lengths of the twomeniscus lenses IV and V are designated respectively F and F Theseaforesaid lenses are so adjusted that the focal length Furthermore, thevalues for refractive index u and the Abb number 1 relating to theoptical materials from which the successive lenses I to VII aremanufactured are given in the table of mathematical expressionsherebelow, wherein the refractive index of the lenses I to VII aredesignated respectively n (I) to n (VII), Abb numbers arecorrespondingly designated 11(1) to v(VII),

f1 G 5 th r 11 m 1 th 1 s ro D(I) 1. 2 Evens group 2 is X e oca eng 0 een g up DGD 1l694 The constructional data relating to the lensthicknesses D( and the air spaces as above mentioned are given in the "Dtable of mathematical expressions given herebelow in terms "I of F whichis the focal length of lens group G "D( 0561 F t 0685 F 6%)f1 I 7 0 0.1748 F t .2136 F .0624 F t .0762 F 40 0 V(V) 50 0 .960 F S 1.l74 F 60.0u(vH) 70'0 .01661 F S .02031 F M 11 630 F S3 770 F ore speci ca y, sa1parameters of the optical system 0249 F S 0305 F are specified 1n thetable of mathematlcal expressions 982 F 1 F given herebelow wherein thedesignations remain the same F S6 857 F 2 ;35 5 r 0438 F 1.397 F S71.707 F 1 R =3.044 F t =.l502 F Stated in another manner, the parametersof the optical R =l.955 F t =.0946 F system may be specified by theaforesaid radii R to R R 568 F 1 :,0946 F the values of said radii beingspecified in the table of math- -R =1.303 F t =.0693 F ematicalexpressions herebelow, the minus sign used R =.824 F t =.1502 F withcertain values applying to surfaces having their cen- R =2.88 F S =l.067F ters of curvature located on the entrant side thereof, R =.954 F S=.01846 F R1 R =.529 F S =.7000 F .579 .717 R =23.09 F S =.0277 F 2 R=23.09 F s =4.42s F R R =28.8 F s =.779 F 1.a5 1.65 R =3.593 F s =1.5s2F n (I)=1.517 v(I)=64.5 R n (II)=l.689 v(II)=30.9 n (III)=l.517v(III)=64.5 n (IV)=1.612 v(IV)=59.5 s n (V)=1.613 v(V)=44.Z E; n(VI)=1.517 v(VI)=64.5

R n (VII)=1.517 v(VII)=64.5 .9 1.1 t =.0623 F u One successful form ofthis invention is specified nu- 7.22 8.82 merically in the chart givenherebelow, wherein the desig- R13 nations for the parameters remain thesame as heretofore,

Magnlfication=5X Afocal Lens System Lens Radii Thicknesses Spaces in; r

S1=46.25 R1 =s4.723 I t1=2.70 1. 517 64. 5

sl=o.0s Ra=84.723 II t1=1.90 1. 689 30. 9

R4 =24.860 III t1=6.50 1. 517 64. 5

--RB =56A94 s==30.30 R5 =35.645 1v t1=4.10 1. 612 59. 5

S4=L20 R; =41.305 vtt=4.10 1. 613 44. 2

S6=1QL45 R10=1000.0 VI. t1=3.00 1.517 64. 5

. 86 33.75 R1:=1247.4 VII t1=6.50 1. 517 64.5

All scalar values given in millimeters.

It will be seen that there is here provided an afocal relay opticalsystem which is capable of superior optical performance at a specifiedprecise image magnification in conformity with the objects of thisinvention and although only a preferred embodiment of this invention hasbeen shown and described in detail, other forms are possible and changesmay be made in the detailed structure of each part thereof within thespecified limitations expressed hereabove without departing from thespirit of the invention as set forth in the claims here appended.

I claim:

1. An afocal relay lens system for forming an image of 5.0xmagnification of an object, said system being especially well correctedfor distortion, field curvature, spherical and chromatic aberration,coma and astigmatism, said system comprising a succession of opticallyali ned lenses which are a front singlet lens designated I which isspaced rearwardly in the direction of entrant light from an object planeby an axial distance which is designated 8; and has an axial thicknessdesignated t;,

a doublet lens which is spaced rearwardly of lens I at a distancedesignated S; and is composed of a front negative lens elementdesignated II and of a rear positive lens element designated III and incontact therewith, the axial thicknesses thereof being designatedrespectively I, and t;,,

a singlet positive meniscus lens designated IV which is spaced from lensIII by a distance S and has an axial thickness designated 1 a singletnegative meniscus lens designated V which is spaced from lens IV by adistance 5, and has an axial thickness designated t a positive singletlens designated VI which is spaced from lens V by an axial distance Sand has an axial thickness represented by t,,

a rearmost positive singlet lens designated VII which is spaced an axialdistance S, from lens VI and has an axial thickness designated b theaxial space rearwardly of lens VII to the image being designated S theoptical parameters governing the construction of said system being setforth in the table of mathematical expressions herebelow in which R; toR represent the successive radii of the refractive surfaces of thelenses I to VII, the minus sign used therewith applying to thosesurfaces having a center of curvature on the entrant side of saidsurfaces, and F designates the focal length of the group of lenses I toV,

the refractive index a of the optical materials in the successive lensesI to VII being designated n (I) to n (VII) and the Abb number 9 of saidoptical materials being designated v(I) to v(VII), the absolute valuesof the refractive indices and Abb numbers being given in the table ofmathematical expressions herebelow,

2. An afocal relay lens system having a distortionless imagemagnification of 5 X along with an excellent correction for allchromatic and monochromatic aberrations, said system comprising inoptical alignment a front double convex singlet lens designated I andspaced at an axial distance which is designated S from an object plane,

-- a doublet lens spaced at a distance S rearwardly of lens I, said lensbeing composed of a negative meniscus lens element designated II andcomposed of a double convex lens element designated II,

a positive meniscus lens designated IV and spaced at a distance fromsaid doublet lens and at a distance S; from a negative meniscus lensdesignated V and located rearwardly thereof, said lenses being convextoward entrant light,

a second double convex singlet lens designated VI and spaced at adistance S rearwardly of lens V, and

a third double convex singlet lens designated VII which is spaced at adistance S from lens VI,

the lens VII being spaced at a distance 5-, from the image formed bysaid system, the constructional data for said optical system beingspecified in the chart herebelow wherein the radii of the successivelenses I to VII numbered in order from the front of the system beingdesignated R to R and the minus sign used therewith applying to thoselens surfaces having their centers of curvature on the entrant sidethereof, the axial thicknesses of the successive lenses I to VII beingdesignated t; to t7, the refractive index and the Abb number of theoptical materials in said lenses being designated respectively n;; andv.

Magnification=5X Afocal Lens System Magnificatlon= 5X Afocal Lens SystemLens Radil Thicknesses Spaces m:

Rl0= 1000.0 VI- tu=3.00 1. 517 64. 5

Sa=33.75 R|z= 1247.4 VII t1=6.50 1. 517 64. 5

All scalar values given in millimeters.

No references cited.

JEWELL H. PEDERSEN, Primary Examiner.

JOHN K. CORBIN, Examiner.

1. AN AFOCAL RELAY LENS SYSTEMS FOR FORMING AN IMAGE OF 5.0XMAGNIFICATION OF AN OBJECT, SAID SYSTEM BEING ESPECIALLY WELL CORRECTEDFOR DISTORTION, FIELD CURVATURE, SPHERICAL AND CHROMATIC ABERRATION,COMA AND ASTIGMATISM, SAID SYSTEM COMPRISING A SUCCESSION OF OPTICALLYALIGNED LENSES WHICH ARE A FRONT SINGLET LENS DESIGNATED I WHICH ISSPACED REARWARDLY IN THE DIRECTION OF ENTRANT LIGHT FROM AN OBJECT PLANEBY AN AXIAL DISTANCE WHICH IS DESIGNATED S1 AND HAS AN AXIAL THICKNESSDESIGNATED T1, A DOUBLET LENS WHICH IS SPACED REARWARDLY OF LENS I AT ADISTANCE DESIGNATED S2 AND IS COMPOSED OF A FRONT NEGATIVE LENS ELEMENTDESIGNATED II AND OF A REAR POSITIVE LENS ELEMENT DESIGNATED III AND INCONTACT THEREWITH, THE AXIAL THICKNESSES THEREOF BEING DESIGNATEDRESPECTIVELY T2 AND T3, A SINGLET POSITIVE MENISCUS LENS DESIGNATED IVWHICH IS SPACED FROM LENS III BY A DISTANCE S3 AND HAS AN AXIALTHICKNESS DESIGNATED T4, A SINGLET NEGATIVE MENISCUS LENS DESIGNATED VWHICH IS SPACED FROM LENS IV BY A DISTANCE S4 AND HAS AN AXIAL THICKNESSDESIGNATED T5, A POSITIVE SINGLET LENS DESIGNATED VI WHICH IS SPACEDFROM LENS V BY AN AXIAL DISTANCE S5 AND HAS AN AXIAL THICKNESSREPRESENTED BY T6, A REARMOST POSITIVE SINGLET LENS DESIGNATED VII WHICHIS SPACED AN AXIAL DISTANCE S6 FROM LENS VI AND HAS AN AXIAL THICKNESSDESIGNATED T7, THE AXIAL SPACE REARWARDLY OF LENS VII TO THE IMAGE BEINGDESIGNATED S7, THE OPTICAL PARAMETERS GOVERNING THE CONSTRUCTION OF SAIDSYSTEM BEING SET FORTH IN THE TABLE OF MATHEMATICAL EXPRESSIONSHEREBELOW IN WHICH R1 TO R13 REPRESENT THE SUCCESSIVE RADII OF THEREFRACTIVE SURFACES OF THE LENSES I TO VII, THE MINUS (-) SIGN USEDTHEREWITH APPLYING TO THOSE SURFACES HAVING A CENTER OF CURVATURE ON THEENTRANT SIDE OF SAID SURFACES, AND F DESIGNATES THE FOCAL LENGTH OF THEGROUP OF LENSES I TO V, THE REFRACTIVE INDEX ND OF THE OPTICAL MATERIALSIN THE SUCCESSIVE LENSES I TO VII BEING DESIGNATED ND(I) TO ND(VII) ANDTHE ABBE'' NUMBER V OF SAID OPTICAL MATERIALS BEING DESIGNATED V(I) TOV(VII), THE ABSOLUTE VALUES OF THE REFRACTIVE INDICES AND ABBE'' NUMBERSBEING GIVEN IN THE TABLE OF MATHEMATICAL EXPRESSIONS HEREBELOW,R1=1.955F T2=.0438F -R2=3.044F T3=.1502F R3=1.595F T4=.0946F R4=.568FT5=.0946F -R5=1.303F T6=.0693F R6=.824F T7=.1502F R7=2.88F S1=1.067FR8=.954F S2=.01846F R9=.529F S3=.7000F R10=23.09F S4=.0277F -R11=23.09FS5=4.425F R12=28.8F S6=.779F -R13=3.593F S7=1.552F ND(I)=1.517 V(I)=64.5ND(II)=1.689 V(II)=30.9 ND(III)=1.689 V(III)=64.5 ND(IV)=1.612V(IV)=59.5 ND(V)=1.613 V(V)=44.2 ND(VI)=1.517 V(VI)=64.5 ND(VII)=1.517V(VII)=64.5 T1=.0623F